Generally, the IRS considered barter income as reportable and taxable. Barter income for services performed is generally self employment income and subject to self employment tax (SET). SET is how the self employed pay their FICA tax. So, you might earn Social security credits for that income.
You can "google' barter as self employment income (or similar wording) and get lots of references, e.g. https://www.forbes.com/2009/11/11/irs-tax-barter-exchange-income-personal-finance-wood.html
Many of the activities, you've suggested, involve gray areas. For example, room and board provided at the convenience of the employer is not taxable. If the organization is an eligible charity, reimbursement of expenses for volunteering would not be taxable. Discounts generally are not income. Totally free, in exchange for services, might have pass muster, depending on all the circumstances.
